intro(1)

NAME

intro − introduction to command utilities and application programs

DESCRIPTION

This section describes commands accessible by users, as opposed to system calls in Section (2) or library routines in Section (3), which are accessible by user programs.

Command Syntax

Unless otherwise noted, commands described in this section accept options and other arguments according to the following syntax:

name [option(s)] [cmd_arg(s)]

where the elements are defined as follows:

name Name of an executable file.

option One or more options can appear on a command line. Each takes one of the following forms:

-no_arg_letter
A single letter representing an option without an argument.

-no_arg_letters
Two or more single-letter options combined into a single command-line argument.

-arg_letter<>opt_arg
A single-letter option followed by a required argument where:

arg_letter
is the single letter representing an option that requires an argument,

opt_arg
is an argument (character string) satisfying the preceding arg_letter,

<> represents optional white space.

cmd_arg Path name (or other command argument) not beginning with -, or - by itself indicating the standard input. If two or more cmd_args appear, they must be separated by white space.

RETURN STATUS

Upon termination, each command returns two bytes of status, one supplied by the system giving the cause for termination, and (in the case of “normal” termination) one supplied by the program (for descriptions, see wait(2) and exit(2)). The system-supplied byte is 0 for normal termination. The byte provided by the program is customarily 0 for successful execution and non-zero to indicate errors or failure such as incorrect parameters in the command line, or bad or inaccessible data. Values returned are usually called variously “exit code”, “exit status”, “return code”, or “return value”, and are described only where special conventions are involved.

WARNINGS

Some commands produce unexpected results when processing files containing null characters. These commands often treat text input lines as strings, and therefore become confused when they encounter a null character (the string terminator) within a line.

Museum